# Tagged Questions

The description of the movement of bodies by their position, velocity, acceleration (and possibly higher time derivatives, such as, jerk) without concern for the underlying dynamics/forces/causes.

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### Finding if two objects collide

The question that I'm trying to understand is this: This is the part of the solution I don't understand: From my knowledge, if $v_p-v_q$ is due south, this means $r_p-r_q$ is also due south, ...
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### Physical pendulum dynamics confusion

I'm validating a Matlab Simulink SimMechanics model analytically. The model consists of a physical pendulum (uniform rod with length $l$ and width $w$) which is torque driven. I'm somewhat confused ...
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### How would you go about solving this tricky distance problem? [closed]

I've tried calculating the distance the runner has left to get to the finish line by the time the bird gets there and adding it to the distance the bird has to fly back to the runner. Then I ...
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### Considering velocity-distance graph [closed]

A car is travelling at constant velocity. Its brakes are then applied, causing uniform deceleration. Which graph shows the variation with distance s of the velocity v of the car? The solution is A, ...
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### How to calculate initial acceleration of a projectile motion? [closed]

I have an object following a projectile motion, that hasn't got horizontal acceleration but only vertical -g. What is the acceleration that I have to use in the second law of motion (F = ma) in order ...
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### Finding the height of a balloon [closed]

A balloon moves up vertically such that if a stone is thrown from it with horizontal velocity $u$ relative to it, the stone always hits the ground at a fixed point $2u^2/g$ horizontally away from it. ...
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### How exactly do objects move

Suppose I have a piece of steel that is made up of one row of 100 atoms. Now, suppose I try to slide it across a surface by pushing it forward, the atom I come into contact with (the last atom in the ...
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### Equations of motion acceleration doubt

So i was going through some text today morning. Where it said $$a = \frac{vdv}{dx}$$ So they then went on to, $$vdv = adx \\ \implies \int vdv = \int adx$$ But,I am very certain acceleration is ...
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### Equations of motion derivation doubt

I just started on learning how to derive the equations of motion using calculus. This is my first time and I have a basic doubt. So $v = \large{\frac{dx}{dt}}$ Then, $dx = v dt$ What does this ...
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### Components of Velocity in polar co-ordinates

Consider a point moving along a curve in a plane. The position of a point P on a coordinate system can be specified by a single vector $\vec{r}$=$r\hat{r}$. A rough sketch describing the situation is ...
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### Can velocity be negative? [closed]

In free fall I use the formula V=g*t and g is negative(-9.8m/s^2). It gives me negative.
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### Derivation of centripetal acceleration

While reading HC Verma chapter 7 circular motion I came across a derivation which I couldnt understand. I have marked my doubt with red. I don't understand from where +dw/dt [- i sine +j cos0] came ...
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### If two cars have the same acceleration at time $t$, are the velocities of the cars the same at time $t$?

So when I look at the question logically, I reason that if I had two cars: Range Rover and BMW, at time t, I could pump the gas and make them accelerate at the same rate at 0.5 m/s^2 but I could be ...
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### Watching Airplanes Fly Toward You

Recently, I was enjoying the stars on a cool summer night and saw an airplane flying toward me from the distance. I observed its path as it started out as a small dot in the distance until it flew ...
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### How do they know their velocity in a spaceship? [closed]

Suppose a spaceship is going to Mars or to Jupiter, they switch on their thrusters and accelerate for a certain period, how to they know their position / velocity, do they refer to the Sun?